﻿1036 
  Forty-seventh 
  Report 
  on 
  the 
  State 
  Museum. 
  

  

  Lycophoria, 
  Lahusen. 
  1885. 
  

   (Plate 
  45, 
  figs. 
  36-38.) 
  

  

  Yalves 
  rotund 
  and 
  without 
  median 
  fold 
  or 
  sinus, 
  so 
  that 
  the 
  

   anterior 
  margin 
  of 
  contact 
  is 
  almost 
  straight, 
  or 
  very 
  gently- 
  

   sinuous. 
  Beaks 
  full 
  and 
  closely 
  incurved, 
  only 
  the 
  pedicle-valve 
  

   appearing 
  to 
  have 
  retained 
  a 
  foramen, 
  though 
  the 
  cardinal 
  area 
  

   is 
  present 
  in 
  both. 
  The 
  brachial 
  valve 
  bears 
  a 
  hinge-plate 
  which 
  

   is 
  recurved 
  into 
  the 
  pedicle-cavity 
  of 
  the 
  opposite 
  valve, 
  and 
  is 
  

   produced 
  into 
  a 
  long, 
  curved 
  cardinal 
  process, 
  bifurcate 
  at 
  its 
  

   extremity. 
  The 
  crural 
  plates 
  are 
  connected 
  with 
  the 
  elevated 
  

   margins 
  of 
  the 
  four 
  adductor 
  impressions. 
  In 
  the 
  opposite 
  valve 
  

   the 
  teeth 
  are 
  supported 
  by 
  divergent 
  plates 
  which 
  extend 
  for- 
  

   ward 
  for 
  about 
  one-half 
  the 
  length 
  of 
  the 
  shell 
  and 
  rest 
  upon 
  the 
  

   bottom 
  of 
  the 
  valve. 
  Externally 
  the 
  shell 
  is 
  smooth 
  in 
  the 
  

   umbonal 
  regions, 
  but 
  anteriorly 
  is 
  covered 
  with 
  low, 
  rounded 
  

   plications 
  crossed 
  by 
  fine 
  concentric 
  lines. 
  

  

  Type, 
  Lycophoria 
  micella, 
  Dalman 
  (sp.). 
  

  

  Distribution. 
  Lower 
  Silurian. 
  

  

  Conchidium, 
  Linne. 
  1753. 
  

   (Plate 
  46, 
  figs. 
  1-14.) 
  

  

  Synonyms; 
  Gypidia, 
  Dalman, 
  1828; 
  Zdimir, 
  Barrande, 
  1881; 
  

   Antirhynchonella, 
  Quenstedt, 
  1871. 
  

  

  Shells 
  elongate- 
  subtrigonal 
  or 
  sub 
  pentagonal 
  in 
  outline, 
  strongly 
  

   inequivalve, 
  biconvex 
  ; 
  median 
  fold 
  and 
  sinus 
  faint, 
  if 
  at 
  all 
  

   developed. 
  Anterior 
  margins 
  of 
  contact 
  usually 
  straight, 
  with 
  

   sometimes 
  a 
  faint 
  fold, 
  at 
  others 
  a 
  low 
  sinus 
  on 
  both 
  valves. 
  

   Surface 
  with 
  numerous 
  sharp 
  or 
  rounded, 
  simple 
  or 
  divided 
  

   plications 
  extending 
  from 
  beaks 
  to 
  margins; 
  cardinal 
  slopes 
  

   broad 
  and 
  usually 
  smooth. 
  

  

  In 
  the 
  pedicle-valve 
  the 
  umbo 
  is 
  elevated, 
  attenuated, 
  more 
  or 
  

   less 
  incurved, 
  not 
  prone 
  upon 
  the 
  opposite 
  valve. 
  No 
  cardinal 
  

   area 
  is 
  developed. 
  The 
  delthyrium 
  is 
  very 
  broad 
  and 
  bears 
  a 
  

   concave 
  deltidium, 
  which, 
  however, 
  is 
  frequently 
  wanting. 
  

   Teeth 
  small, 
  supported 
  by 
  convergent 
  iamellae 
  which 
  unite 
  in 
  

   the 
  interior 
  cavity 
  and 
  form 
  a 
  single 
  median 
  vertical 
  septum 
  of 
  

   variable 
  length 
  ; 
  in 
  the 
  typical 
  species 
  usually 
  extending 
  almost, 
  

   and 
  sometimes 
  quite 
  to 
  the 
  anterior 
  margin, 
  and 
  vertically, 
  for 
  

  

  94 
  

  

  